Cholera - an acute intestinal infection

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Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. It has a short incubation period and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients.

Most persons infected with V. cholerae do not become ill, although the bacterium is present in their faeces for 7-14 days. When illness does occur, about 80-90% of episodes are of mild or moderate severity and are difficult to distinguish clinically from other types of acute diarrhoea. Less than 20% of ill persons develop typical cholera with signs of moderate or severe dehydration.

Cholera remains a global threat and is one of the key indicators of social development. While the disease no longer poses a threat to countries with minimum standards of hygiene, it remains a challenge to countries where access to safe drinking water and adequate sanitation cannot be guaranteed. Almost every developing country faces cholera outbreaks or the threat of a cholera epidemic.

Сholera is typically transmitted by either contaminated food or water. In the developed world seafood is the usual cause while in the developing world it is more often water. Cholera has been found in only two other animal populations: shellfish and plankton.

Although cholera may be life-threatening, prevention of the disease is normally straightforward if proper sanitation practices are followed. In developed countries, due to nearly universal advanced water treatment and sanitation practices, cholera is no longer a major health threat. The last major outbreak of cholera in the United States occurred in 1910-1911.Effective sanitation practices, if instituted and adhered to in time, are usually sufficient to stop an epidemic. There are several points along the cholera transmission path at which its spread may be halted:

· Sterilization

· Sewage

· Sources

· Water purification

Cholera likely has its origins in the Indian subcontinent. The disease first spread by trade routes (land and sea) to Russia in the 1817, then to Western Europe, and from Europe to North America.

Pandemics

· 1816-1826 - First cholera pandemic

· 1961-Present - Seventh cholera pandemic began in Indonesia, called El Torafter the strain, and reached East Pakistan (now Bangladesh) in 1963, India in 1964, and the USSR in 1966. From North Africa it spread into Italy by 1973. In the late 1970s, there were small outbreaks in Japan and in the South Pacific. There were also many reports of a cholera outbreak near Baku in 1972

Notable outbreaks

By 12 February 2009, the number of cases of infection by cholera in sub-Saharan Africa had reached 128,548 and the number of fatalities, 4,053.

· October 2010 - In late October a cholera outbreak was reported in Haiti and as of November 16th the Haitian Health Ministry reported that the number of dead has surpassed 1000. The ministry's latest numbers as of Nov. 14 show the number of dead rising to 917, from 724 on November 12, with hospitalizations for cholera symptoms totalling 14,642.It is feared that the epidemic could accelerate due to standing water left by a recent hurricane and the fact that over one-tenth of the population remain living in close quarters in tents in refugee camps without adequate sanitation since the Haiti earthquake in January.

· August 2010 - Nigeria is reaching epidemic proportions after wide spread confirmation of the Cholera outbreaks in 12 of its 36 states. 6400 cases have been reported with 352 reported deaths. The health ministry blamed the outbreak on heavy seasonal rainfall and poor sanitation.

· January 2009 - The Mpumalanga province of South Africa has confirmed over 381 new cases of Cholera, bringing the total number of cases treated since November 2008 to 2276. 19 peoplehavediedintheprovincesincetheoutbreak.

· August 2008 - April 2009: In the 2008 Zimbabwean cholera outbreak, which is still continuing, an estimated 96,591 people in the country have been infected with cholera and, by 16 April 2009, 4,201 deaths had been reported.http://en.wikipedia.org/wiki/Cholera - cite_note-WHO_Zimbabwe_2009-58 According to the World Health Organization, during the week of 22-28 March 2009, the "Crude Case Fatality Ratio (CFR)" had dropped from 4.2% to 3.7%.The daily updates for the period 29 March 2009 to 7 April 2009, list 1748 cases and 64 fatalities, giving a weekly CFR of 3.66% (see table above);however, those for the period 8 April to 16 April list 1375 new cases and 62 deaths (and a resulting CFR of 4.5%).The CFR had remained above 4.7% for most of January and early February 2009.

· November 2008 - Doctors Without Borders reported an outbreak in a refugee camp in the Democratic Republic of the Congo's eastern provincial capital of Goma. Some 45 caseswerereportedlytreatedbetweenNovember 7 through 9th.

· August - October 2008 - As of 29 October 2008, a total of 644 laboratory-confirmed cholera cases, including eight deaths, had been verified in Iraq.

· March - April 2008 - 2,490 people from 20 provinces throughout Vietnam have been hospitalized with acute diarrhea. Ofthosehospitalized, 377 patientstestedpositiveforcholera.

· August 2007 - The cholera epidemic started in Orissa, India. The outbreak has affected Rayagada, Koraput and Kalahandi districts where more than 2,000 people have been admitted to hospitals.

· July - December 2007 - A lack of clean drinking water in Iraq has led to an outbreak of cholera.As of 2 December 2007, the UN has reported 22 deaths and 4,569 laboratory-confirmed cases.

· In 2000, some 140,000 cholera cases were officially notified to WHO. Africaaccountedfor 87% ofthesecases.

· January 1991 to September 1994 - Outbreak in South America, apparently initiated when a ship discharged ballast water. Beginning in Peru there were 1.04 million identified cases and almost 10,000 deaths. The causative agent was an O1, El Tor strain, with small differences from the seventh pandemic strain. In 1992 a new strain appeared in Asia, a non-O1, nonagglutinable vibrio (NAG) named O139 Bengal. It was first identified in Tamil Nadu, India and for a while displaced El Tor in southern Asia before decreasing in prevalence from 1995 to around 10% of all cases. It is considered to be an intermediate between El Tor and the classic strain and occurs in a new serogroup. There is evidence of the emergence of wide-spectrum resistance to drugs such as trimethoprim, sulfamethoxazole and streptomycin.

Research cholera intestinal infection

The Russian-born bacteriologist WaldemarHaffkine developed the first cholera vaccine around 1900. The bacterium had been originally isolated forty five years earlier (1855) by Italian anatomist FilippoPacini, but its exact nature and his results were not widely known around the world.

One of the major contributions to fighting cholera was made by the physician and pioneer medical scientist John Snow (1813-1858), who found a link between cholera and contaminated drinking water in 1854.Dr Snow proposed a microbial origin for epidemic cholera in 1849. In his major "state of the art" review of 1855, he proposed a substantially complete and correct model for the aetiology of the disease. In two pioneering epidemiological field-studies, he was able to demonstrate that human sewage contamination was the most probable disease vector in two major epidemics in London in 1854. His model was not immediately accepted, but it was seen to be the more plausible as medical microbiology developed over the next thirty years or so.

Cities in developed nations made massive investment in clean water supply and well-separated sewage treatment infractures was made between the mid-1850s and the 1900s. This eliminated the threat of cholera epidemics from the major developed cities in the world. Robert Koch, 30 years later, identified V. cholerae with a microscope as the bacillus causing the disease in 1885.

Cholera has been a laboratory for the study of evolution of virulence. The province of Bengal in British India was partitioned into West Bengal and East Pakistan in 1947. Prior to partition, both regions had cholera pathogens with similar characteristics. After 1947, India made more progress on public health than East Pakistan (now Bangladesh). As a consequence,the strains of the pathogen that succeeded in India had a greater incentive in the longevity of the host. They have become less virulent than the strains prevailing in Bangladesh. These uninhibitedly draw upon the resources of the host population, thus rapidly killing many victims.

More recently, in 2002, Alam et al. studied stool samples from patients at the International Centre for Diarrhoeal Disease (ICDDR) in Dhaka, Bangladesh. From the various experiments they conducted, the researchers found a correlation between the passage of V. cholerae through the human digestive system and an increased infectivity state. Furthermore, the researchers found that the bacterium creates a hyper-infected state where genes that control biosynthesis of amino acids, iron uptake systems, and formation of periplasmic nitrate reductase complexes were induced just before defecation. These induced characteristics allow the cholera vibrios to survive in the "rice water" stools, an environment of limited oxygen and iron, of patients with a cholera infection.^[72]

Notable cases

· Tchaikovsky's death has traditionally been attributed to cholera, most probably contracted through drinking contaminated water several days earlier.Since the water was not boiled and cholera was once again rampaging St. Petersburg, such a connection was quite plausible ...."^[74] However, some, including English musicologist and Tchaikovsky authority David Brown and biographer Anthony Holden, have theorized that his death was a suicide.It should be noted also that Tchaikovsky's mother died of cholera, -75 and his father became sick with cholera at this time but made a full recovery.

· Elliott Frost, son of American poet Robert Frost

· Following the devastating earthquake on January 12, 2010 in Haiti, a cholera outbreak began to spread rapidly in October 2010.http://en.wikipedia.org/wiki/Cholera - cite_note-78 While the death toll has surpassed 900 in Haiti, another outbreak in Nigeria is reaching 2000.

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